.TH std::nullopt_t 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::nullopt_t \- std::nullopt_t

.SH Synopsis
   Defined in header <optional>
   struct nullopt_t;             \fI(since C++17)\fP

   std::nullopt_t is an empty class type used to indicate optional type with
   uninitialized state. In particular, std::optional has a constructor with nullopt_t
   as a single argument, which creates an optional that does not contain a value.

   std::nullopt_t must be a non-aggregate LiteralType and cannot have a default
   constructor or an initializer-list constructor.

   It must have a constexpr constructor that takes some implementation-defined literal
   type.

.SH Notes

   The constraints on nullopt_t's constructors exist to support both op = {}; and op =
   nullopt; as the syntax for disengaging an optional object.

   A possible implementation of this class is

 struct nullopt_t {
     constexpr explicit nullopt_t(int) {}
 };

.SH See also

   nullopt an object of type nullopt_t
   \fI(C++17)\fP (constant)
